Stretch bending machine with segmental die,tolerance detector,and safety shock absorber



Aug. 25, 1970 Q RAUER ET AL 3,525,247

TOLERANCE STRETCH BENDING MACHINE WITH SEGMENTAL DIE,

DETECTOR, AND SAFETY SHOCK ABSORBER .4 Sheets-Sheet 1 Filed Jan. 8, 1968Aug. 25, 1970 E H BRAUER ET AL 3,525,247

STRETCH BENDING MACHINE WITH SEGMENTAL DIE, TOLERANCE DETECTOR, ANDSAFETY SHOCK ABSORBER Filed Jan. 8, 1968 .4 Sheets-Sheet 2 INVENTOR. I'm% I I 44 ATTORNEY Aug. 25, 1970 E H. BRAUER ETAL STRETCH SENDINGMACHINE WITH SEGMENTAL DIE, TOLERANCE Filed Jan. 8, 1968 DETECTOR, ANDSAFETY SHOCK ABSORBER .4 Sheets-Sheet 5 C v SUPPLY INVENTOR.

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I 3 22 ATTOENEK 3,525,247 TOLERANCE 25, 1970 E. H, BRAUER E STRETCHBENDING MACH]:

NE WITH SEGMENTAL DIE,

DETECTOR, AND SAFETY SHOCK ABSORBER .4 Shegts-Sheet 4.

Filed Jan. 8, 1968 INVENTOR. M 71 ,4

9+ ATTOEWEK United States Patent ABSTRACT on THE DISCLOSURE The presentmachine is one by which a structural member, such as an I-beam, channel,plate, or the like, can be formed into curvilinear shape by bending ittransversely of its length into conformance with a segmental curvilineardie while tensioning it endwise into its yield range. Tension applyingdevices grip opposite ends of the member for applying the requiredtension and are movable back and forth in a path extending transverselyof the length of the die so as to lay the member onto the diesegmentswhile the tension is maintained. The segments are adjustable todifferent positions, for forming bends of different radii, by powerdevices controlled by a numerical control or programmer such thatrepositioning of the die segments for each different selected shape canbe effected quickly.

The improvements herein are as follows:

A shock absorbing device combined with a tension applying device forreducing shocks in the event of breakage of the member being tensioned.

Error indicator means which, when the member is formed, checks the shapeof the member at a number of stations, such as at each die segment, andindicates conformance and non-conformance, and the extent to which thenon-conformance is above or below tolerance limits. This checking may beeffected while the member remains under tension or after the tension isrelieved.

Brakes are provided for locking each die segment against creepage uponits reaching its programmed position.

This invention is an improvement on the invention disclosed in theco-pending application of Edwin H. Brauer and T. Virgil Huggett, Ser.No. 612,982, filed Jan. 31, 1967, now Pat. No. 3,426,569, and entitledStretch Forming Machine and Segmental Adjustable Die Combination. Thisinvention relates to a stretching machine, and particularly to a stretchbending machine for bending rolled structural members, such as I-beams,channels, bulb beams, and the like.

As more fully disclosed in the above-entitled application, the machineis one by which the structural members can be bent transversely of theirlength against a curvilinear segmental die into curvilinear form whiletensioned into their yield range. The segments are adjustable, each toits desired position, by power means controlled by numerical control,and the segment faces can be positioned thereby to define selectivelycurves which are concave at one side only or are in the form of S orreverse curves.

In such machines, upon release of the member after bending, there is atendency for spring-back to a degree beyond selected tolerances. Evenduring forming it may occur that certain portions of the piece do notengage the die segments as intended. In accordance with the presentinvention, the failure to engage any selected one of hte die segments orto spring back from engagement therewith beyond tolerable limits uponrelease of the tensioning forces is detected at each of a plurality ofstations along 3,525,241 Patented Aug. 25, 1970 the die, selectively,usually one station at each die segment. Whether the beam engages theparticular segment, or springs back, within the preselected tolerancelimits, and whether the error is above or below tolerance, is indicated.This detection may be effected either during tensioning and bending orupon release of the tensioning force, as desired.

Again, since the heavy beams, such as ship ribs and the like, are beingstretched and bent, extremely high forces are developed which, uponbreakage of the member, release tremendous absorbed energy which isreflected in the stretching devices. In accordance with the presentinvention these forces are absorbed by shock absorbers operable by thefluid in the hydraulic stretching devices.

There also exists the tendency of vibration occurring as a result ofstretching and releasing of the workpiece and the like to cause the diesegments to creep along the driving screws which move them to theirrespective positions. This creepage is eliminated.

Various other objects and advantages of the invention will becomeapparent from the following description wherein reference is made to thedrawings, in which:

FIG. 1 is a diagrammatic top plan view of a machine embodying theprinciples of the present invention;

FIG. 2 is an enlarged fragmentary longitudinal sectional view of one ofthe stretching piston and cylinder assemblages of the invention;

FIG. 3 is an enlarged fragmentary side elevation of one of the diesegments and supporting equipment, as indicated by the line 33 in FIG.1, part thereof being shown in section to disclose the error detectormechanism;

FIG. 4 is a diagrammatic illustration of the electrical circuitry usedin the present invention;

FIG. 5 is an enlarged wiring diagram showing in more detail theelectrical circuitry and connections of the detecting and indicatingdevices illustrated generally in FIG. 4; and

FIG. 6 is a diagrammatical illustration of a modified form of shockabsorber used in the present invention.

Referring to the drawings, the machine comprises a rigid bed 1 whichsupports a segmental die and stretch units. The segmental die comprisesa plurality of individually adjustable die segments 2 each of Which isto be adjusted along a lineal path transversely of the bed 1 to aposition selected in accordance with the curvatures desired in themember to be stretch bent. To provide for such adjustment, suitableguideways 3 are mounted on the bed extending transversely thereof, anddie carriages 4 are mounted in the guideways for movement lineallytherealong. Each of the carriages 4 carries a die segment 5 having anoperating face 6 against which a structural member or beam S is to bebent. For adjusting each carriage along the guideways 3, a feed screw 7,driven by a reversible D-C servo-motor 8, is drivingly connected to afollower 9 on the carriage.

As described in the above co-pending application, the servo-motors 8 arecontrolled by a numerical control or a programmer for positioning thecarriages 4, and hence the die segment 5, in their respective positions.

Each of the reversible servo-motors 8 rotates its associated one of thefeed screws 7 at selected speeds for a predetermined number of rotationsdictated by the programmer. The shaft of the motor 8, in turn, drives afeedback unit 11. The feed-back unit supplies signals through a conduit12 to a numerical control unit which includes a servo amplifier 13, atape reader 14, through which a tape 15 is fed, and an interpolator 16.The servo amplifier 13 receives the signal from the feed-back unit 11and receives command signals from the interpolator 16. The tape has beenprepared for a predetermined setting of the die segments and its outputcommand signals are a function of perforations in the pre-programmedtape. The servo amplifier 13 compares the command signals from theinterpolator 16 with the output signals from the motor feed-back unit 11and controls the motor accordingly in a well known manner. Thisparticular type of numerical control is well known and available on themarket. Adjustment of each carrier, and hence its associated diesegment, is continued by the control until the command and feed-backsignals are in balance, whereupon the associated carrier 4 is stopped.Conventional switch means, not shown, are built into the numericalcontrol unit and arranged so that, as each servo-motor 8 drives itsfollower to dictated position, the switch means connect the numericalcontrol unit to the next succeeding servo-motor 8 and associatedfeed-back 11. Thus, the functions of the motors 8 are carried outsuccessively until all of the segments are in their preselectedpositions. Thus they may be readily moved to the proper position, andstopped therein, in response to the tape.

The feed screw is preferably self-locking against rotation by forcesimposed on the carrier 4 and by vibrations and the like in the machine.However, in order to eliminate any possible creepage due to slightrotation of the screw 7 under the influence of these vibrations, brakes18 are connected to the screws 7, respectively.

Each brake 18 may be a conventional spring applied magnetically releasedbrake with the coil connected in parallel with the associated motor 8through a suitable time delay (not shown) so that the coil of the brakeis energized and the brake released so long as the motor is energized,and is applied, after a slight time delay, when the motor 8 isdeenergized.

The specific brake structure and the wiring for this arrangement and forcontrolling the motor by a numerical control may be conventional.

In order to apply tensioning forces to the ends of the workpiece S,stretching assemblages 18 are mounted on the bed 1, one at each end, asmore fully set forth in the above-mentioned co-pending application.

Briefly, each stretch forming assemblage comprises a supporting carriage20 having suitable rollers 21 operated in trackways 22 on the bed 1 andextending lineally transversely in the bed so that the carriage 20 canbe driven transversely of the bed. Each carriage 20 is driventransversely of the bed by a suitable screw 23 driven, in turn, by areversible motor 24 through reduction gearing 25. Each carriage carriesa platform 27 which is secured to the carriage by an upright pivot 28 sothat the platform 27 can swing about the axis of the pivot 28 relativeto the carriage 20. The rear of the platform 27 rides on suitableslideways 29.

Secured in fixed position on the platform 27 for swinging therewithabout the axis of the pivot 28 is a horizontal reversible piston andcylinder assemblage 30 comprising a cylinder 31 in which is disposed apiston 32 having a rod 33. A stretch head 34 for gripping the end of themember S to be bent and applying tension thereto is connected bysuitable yoke and pivot device 35 to the piston rod 33. Thus, forbending the workpiece, tension into the yield range of the member S isapplied by the head 34 and, while the tension is applied, the carriage20 is moved transversely of the bed in the direction or of tensioningforce so as to lay the stock against the faces of the die segments. Thestretch forming assemblages 18 are identical.

If desired, tension controls may be provided, in which case the grippingheads would be supported as described in U.S. Pat. No. 3,052,119 toCyril J. Bath and No. 3,302,437 to Stanley M. Dolney.

As mentioned heretofore, it is desirable in the event of breakage of themember S, that the shock be absorbed. As best illustrated in FIG. 2,pressure fluid is applied to the reversible piston and cylinderassemblage 30 by a pump 37 driven by a motor 38. The supply iscontrolled by a stop and reversing valve 39. A pipe line 40 leads fromone port of the valve to the rod end of the cylinder 31, and a line 41leads from the other port of the valve to the head end of the piston 32.The intake and outlet ports of the pump are connected to the valve 39,and a sump 42 is also connected to the pump intake port. In normaloperation, the piston 32 can be advanced, retracted, or stopped andlocked hydraulically, all by operation of the valve 39. The Valvepreferably is solenoid operated for remote control.

It is apparent that when the workpiece is under extremely hightensioning forces due to the introduction of pressure fluid into the rodend of the cylinder 31, a tremendous amount of energy is stored in themember S and the various stressed parts of the machine, particularly thestretch assemblage. If, while in this condition, the member S shouldbreak, or slip out of the gripping jaws, this energy would be reflectedin driving of the piston 32 rapidly to the head end of its cylinder 31,which is to the left in FIG. 2. Normally the piston 32 would strike thehead end of the cylinder 31 or the yoke and pivot device 35 would strikethe rod end with a severe impact, thus transferring or applyingdestructive forces to the stretch forming assemblages and supportingparts.

In order to relieve shocks if either of these conditions should occur, acheck valve device 45 is interposed in the line 41 between the valve 39and the head end of the cylinder 31. The device 45 is one of which thevalve is normally closed, but can be opened by pressure deliveredthrough the line 41 from the valve 39 to the head end of the cylinder31. However, a conventional control de vice 46 is provided and isconnected in the circuit to the cylinder 31 and the check device 45 soas to maintain the check valve of the device 45 open so long as thetensioning pressure in the rod end of the cylinder 31 is greater thanthe return pressure in the head end of the cylinder 31. Thus, in normaloperation, the stretch head of the piston 32 can be retracted forapplying tensioning forces by admission of pressure fluid through theline 40 to the rod end of the cylinder and discharge of fluid from thehead end through the then open check valve device 45 and line 41.

To restore the piston 32 to the right in FIG. 2, the valve 39 isoperated to reverse the flow of fluid from the pump 37, and deliverpressure fluid through the line 41 which unseats the value 45, andallows the return of pressure through the line 40 to the sump 42 or pump37.

In the event of release of stored energy and inertial forces uponbreakage of the workpiece, the piston 32, rod 33, and head 34 wouldbegin rapid movement to the left in FIG. 2, and the pressure in the rodend of the cylinder 30 would drop suddenly below normal. This drop inpressure, however, would cause the check valve device 45 to stop, orgreatly reduce, instantly, the escape of pressure fluid through the line41 from the head end of the cylinder 31, so that the fluid at the headend is, in operating effect, entrapped totally or to a suflicient degreeto cause a rapid build up of pressure in the head end of the cylinder101.

This entrapped fluid is used in absorbing shocks. For this purpose, thehead end of the cylinder 31 is provided with a passage 50 which leadsinto an adjacent end of a supplemental cylinder 51. A piston 52 isreciprocable in the cylinder 51 and is normally held in sealing relationto the outer end of the passage 50 by means of high pressure expansibleand contractible fluid, such as nitrogen which is entrapped in thecylinder 51 behind the piston 52. Thus, as the piston 32 starts totravel to the left, the otherwise trapped fluid in the head end of thecylinder 31 is applied to the piston 52 and drives it to the leftagainst the increasing pressure of the entrapped initially high pressurenitrogen. The resistance of the piston 52 to movement to the leftincreases as it approaches the closed end of the cylinder 51 andprogressively increases the compression of the fluid therein. As

a result, the piston 32 is constrained to return toward the head end ofthe cylinder 31 against the resistance of a relatively heavy pressurewhich progressively increases as the piston 32 approaches the head endof the cylinder 31. By this arrangement severe shocks are eliminated.

It is desirable also to check the condition of the workpiece or member Sto determine whether or not it is within the proper tolerances and, ifnot, to adjust the die segments to bring it within such tolerance. Forthis purpose, an error indicting means, as shown in FIGS. 3, 4, and 5,is provided and comprises a plurality of sensing devices, preferably onefor each die segment. Each device includes a sensing pin or probe 60reciprocable in a bore in its associated segment 5. The probe 60 isurged by a spring 61 endwise so that its forward end, if unresisted, canpass outwardly beyond the operating face 6 of its associated die segment5. The probe 60 is connected to signal producing means such as a linearvariable differential transducer 62. The transducer 62 has an armature63 which is connected to the probe in coaxial relation thereto and formovement therewith. The transducer may be of the conventional typehaving a primary winding 65 connected across the low voltage A-C source,indicated by the lines Al-AZ. The transducer has a secondary 66, theterminals of which are connected by conductors 67 and 68, respectively,to the opposite terminals of an A-C signal coil 69 of a signalresponsive means. A resistance 70 is connected across the conductors 67and 68. The signal responsive means includes an error indicator 71having a coil 72, one terminal of which is connected by a conductor 73to a 115 volt D-C supply 74 which may be of a conventional type. Theother terminal of the coil 72 is connected to a pivoted conductor 75which swings, in accordance with the signals received from the coil 69,clockwise and counterclockwise, respectively. The conductor 75 carries acontact 76 which is engageable with stationary contacts 77 and 78,respectively, depending upon whether the conductor arm 75 swings beyonda predetermined distance clockwise or counter-clockwise in response tothe signals received from the transducer. The contacts 77 and 78 areconnected in parallel to a conductor 79 connected to the D-C supply 74.The coil 80 of a control relay is connected in series with one terminalof the supply 74 and the stationary contacts 77 and 78.

A selector switch 85 is provided and has a swinging contact arm 86connected to the conductor 68 between the error indicator 71 and thetransducer 62. The switch 85 has a plurality of individual contacts 87each of which is connected to one of the conductors 68 leading to one ofthe transducers 62. Thus, upon swinging of the arm 86 into contact withany selected contact 87, a circuit is established between the errorindicator 71 and the selected one of the transducers 62 associated withthe particular contact 87. Then, if the selected transducer is moved byits spring 62 to a position beyond that allowed or to a position lessthan that allowed, a signal is produced which is transmitted to theerror indicator 71 and which, if the signal is due to exceeding andfalling short of the tolerance preselected, causes the conductor arm 75to swing to one side or the other of its normal position midway betweenthe stationary contacts 77 and 78. If the signal is great enough ineither instance so that the contactor 76 makes contact with one of thestationary contacts 77 or 78, the control relay coil 80 is energized forclosing a circuit which indicates that an error in tolerance occurs. Forindicating the occurrence of an error, a plurality of error indicatinglights 88, one for each transducer, are provided. These lights areconnectable across 115 volt, 60 cycle A-C source, indicated by the linesL1L2. Each light 88 has one terminal connected to the line L2 and theother terminal connected to a common line 89 which in turn isconnectable to the line L1 through a normally open contact 90 of thecontrol relay 80 when both the contact 90 and a normally open ON and OFFswitch 91 are closed. Interposed between the terminal of each light 88and the line 89 is a switch portion of the connector switch whichcomprises a common selector swinging arm contact 92 connected to theline 89 and operable to engage the contacts 93, respectively, which areconnected to the terminals of the lights 88, respectively, so that eachlight selectively can be connected across the lines L1 and L2 uponclosure of the common contact 92 with the particular contact 83associated with the light. However, if there is insufficient signal tomake contact between the contact 76 and one of the contacts 77 and 78,the normally open relay contacts 90 remain open and no error isindicated. If the signal is beyond tolerance, then contact by thecontactor 76 with either contactor 77 or 78 energizes the control relayclosing its contacts and establishing through the selected one of thelights 88.

Preferably the arms 86 and 92 are mounted on a common shaft and hencerotate together in fixed position relative to each other so that thecircuit established by the arm 92 and contact 93 and any particularlight 88 is established at the same time that a circuit is establishedthrough the contact 86 and the contact 87 to the transducer representedby the particular light. Thus, either when the formed member S is undertension or after the tension is relieved so that spring-back can occur,the member can be checked as to shape to see Whether it is within thetolerance limits permitted. For this purpose, each given die segment 5can be checked selectively, relative to the workpiece by operating theindicator switch to select the transducer for the selected one of thesegments.

If the light 88 thereof does not operate, the member S falls within thetolerances permitted. If the light operates, then the tolerance isbeyond the limits permitted.

By viewing the error indicator, it can be determined whether the errorin the finished workpiece is due to its being overbent or underbent ateach particular location.

With the tension still released, the die segment at the particularlocation at which the error is indicated may be adjusted accordingly,and the tension reapplied until the piece conforms to the tolerancelimits at each die segment.

Generally the members S are so constant that when the die segments havebeen set to the proper place so that upon the first stretching therequired shape is obtained in one member, succeeding members may beformed without changing the position of the die segments. However, eventhen the selector switch should be operated for each segment to confirmthe fact that the piece is within tolerances or to indicate at whatpoint, if any, and to what degree, it exceeds the tolerances. All ofthis contributes to production of a better and more precise final shape,and a recordable history as to some variations from the norm. If in anyinstance a member must be re-bent at some location, after there-bending, as described above, the tolerances at each of the diesegments should be checked a second time. Again, a check may be made andif some particular segment is not in contact with the die, that segmentshould be repositioned to compensate for the error. When all of the diesegments have been brought to proper position, the part may be regrippedand restretched across the new die setting.

A modified type of shock absorber is illustrated in FIG. 6. For example,a stretch forming piston and cylinder assemblage 100, comparable to theassemblage 30 and having a cylinder 10.1 with a piston 102 operabletherein, may be used. At the head end of the cylinder 101 is the usualport 103 which may be connected to a check valve, check device, and stopand reversing valve, such as heretofore described. The head end of thecylinder 101 is provided with a shock absorbing fixture 104 whichcomprises a cylinder 105 which, at its head end, is provided with aflange 106 by which it is secured to the head end of the cylinder 101.The cylinder 105 has a neck portion 107 which is secured in sealedrelation within the head end closure of the cylinder 101 and which has abore 108 extending therethrough and communicating the interior of thecylinder 105 with the interior of the cylinder 101 at the head end ofthe latter. Within the cylinder 105 is a valving sleeve 109 which iscoaxial with the cylinder and spaced inwardly from the circumferentialwall of the cylinder to provide a surrounding chamber 110. A springrestored piston 1'11 is reciprocable within the sleeve 109 and isprovided with a stem 112 which is exposed in the head end of thecylinder 101. When, due to breakage of a workpiece, the piston 102 movessuddenly toward the head end of the cylinder 101, as hereinbeforedescribed, in connection with BIG. 2, the rod 112 is forced by fluidpressure in the head end of the cylinder 101, or by engagement by thepiston 102, to force the piston 111 to the left within the sleeve 109.The sleeve 109 has a plurality of ports 113 communicating the interiorof the sleeve with the chamber 110. The chamber 110 has a port 114 whichconnects the chamber 110 with a suitable pressure tank 115. The ports113 are graduated either in size, number, or both, or spacing, so thatas the piston 111 is driven to the left within the sleeve 109, theresistance to the escape of fluid from the cylinder 109 increasesprogressively as the piston 111 approaches the left end of the sleeve109. This operates in effect to reduce gradually the released forces andenergy tending to drive the piston 102 to the left, thus reducing theshock for the purposes hereinbefore described. The tank 115 is one inwhich the pressure fluid is maintained under sufiicient air pressure tocause return of the piston 111 to the right in FIG. 6, due to thedilferential in the total effective pressure on the head and rod sidesof the piston 111, after the pressure in the head end of the cylinder101 is reduced to normal.

Having thus described our invention, we claim:

1. In a stretch bending machine:

an elongated curvilinear bending die;

stretching means at the opposite ends of the die, re-

spectively, operable to grip the opposite ends of an elongated memberand tension the member endwise into its yield range, at least one of thestretching means being power driven transversely of the tensioningdimension so as to bend the tensioned member into engagement with aforward forming face of the die;

a plurality of sensing devices distributed along the length of the die,each device being operative to sense the deviation of an adjacentportion of a bent member from conformance with the preselected shape tobe produced by the die at said portion; and

deviation indicating means rendered operative by the sensing devices.

2. The structure according to claim 1 wherein each device includes asignal producing means operative to produce signals representing changesin a preselected condition of the sensing device imposed by changes inthe shape of the bent member, and the indicating means include signalresponsive means which are rendered operative by said signals toindicate changes in said preselected condition, and thereby changes ofthe shape of the workpiece.

3. The structure according to claim 2 wherein each device includes aprobe movable toward and away from the forward face of the die along apredetermined path;

resilient means biasing said probe along said path forwardly from theforming face into positions in which it can be engaged by a member bentabout the die and moved thereby back toward the forming face, and saidpreselected condition being the positions of said probe;

said signal producing means are operated by the probe and reflect theposition of the probe along said path, and

the signal responsive means are rendered operative by said signals toindicate when the probe has moved along said path beyond preselectedlimited positions.

4. The structure according to claim 2 wherein a selector switch isconnected to said devices and to said signal responsive means and isoperable to connect said devices, one at a time, selectively, to saidsignal responsive means.

'5. The structure according to claim 1 wherein the die is a segmentaldie having segments which are individually adjustable to selectedpositions to change the shape defined by the die;

means are provided for the individual segments, re-

spectively, each operable for moving its associated segment topreselected positions independently of the movement of the othersegments; and

said devices are connected to the segments, respectively, each devicefor movement as a unit with its associated segment as its associatedsegment is moved to adjusted positions.

References Cited UNITED STATES PATENTS 2,850,071 9/1958 Kraybill 72973,365,921 1/1968 Dolney 72-12 2,457,483 12/1948 Martin 72297 2,553,0925/1951 Hubbert 72-10 3,328,995 7/1967 Rohlfs 72297 3,426,569 2/1969Brauer et a1. 72295 CHARLES W. LANHAM, Primary Examiner M. J. KEENAN,Assistant Examiner US. Cl. X.R.

